Alfalfa/Grass Mixtures Look Promising on MN Farms

Paul Peterson, Extension Forage Agronomist

August 20, 2010

Through July 2010, alfalfa/grass mixture plots on an Otter Tail County farm have already averaged 4.4 ton of forage dry matter (DM) per acre totaled over three harvests: May 20, June 22, and July 28 (Table 1). The plots were seeded August 29, 2008 on the John Wold farm near Underwood and harvested four times during their first production year in 2009.

Similar plots on the Red Cedar (Bill Hard) Farm near Hutchinson have averaged 3.6 ton DM/acre in 2010 so far over three harvests: May 28, June 29, and July 29 (Table 2). These plots were seeded August 25, 2009 and harvested three times in 2009. The Underwood plots are averaging 29% grass in 2010, while the Hutchinson plots only 11% grass. Both sets of plots will be harvested a fourth time in October.

First production year yields in 2009 at both the Underwood and Hutchinson farms was disappointing, averaging less than 3 ton DM/acre, due to suboptimal growing conditions and fertility. So far, 2010 has brought optimum forage growing conditions, and we have stepped up fertility to ensure high levels of P and K.

Boron and ammonium sulfate have also been applied to provide about 3, 45, and 50 lb/acre of B, N, and S, respectively, in 2010. An additional 45 lb N/acre has been applied via urea (Underwood) or ammonium nitrate (Hutchinson). The N was applied in April and after 3rd cutting. The concept is to apply N when the grass component is likely to be most responsive; i.e., spring and late summer/fall.

A third research site was seeded May 4, 2009 on an Avon farm with somewhat harsh soil conditions; a droughty, low organic-matter sand with fairly low initial fertility and moderately low pH. It was mowed a couple times during 2009 to control weeds. Though stands looked very questionable during 2009, they emerged looking very good in 2010. Two harvests have been obtained so far in 2010; May 25 and July 2.

The harshness of the Avon site is evidenced in the 1.8 ton DM/acre yield so far, considerably less than the other two farms. In addition, grass content at Avon (averaging 52%) is greater, as alfalfa growth there is clearly limited. Red clover/grass mixtures seeded at that site suggest that red clover may be better suited than alfalfa.

A few observations so far about specific grass options:

Mixtures with orchardgrass or tall fescue have been among the most consistently productive to date.

There is considerable varietal variation within grass species (data not shown); so as with alfalfa, variety selection is important in grasses too.

Mixtures with timothy have generally been low yielding. Timothy was seeded at 4 lb/acre in mixtures, likely too much given its relatively small seed, so alfalfa establishment was suppressed in its mixtures. This is interesting because while timothy is not a competitive grass once established, it was too competitive during establishment when seeded too heavily.

In addition to an October 2010 cutting, plots will be harvested through at least 2011. Forage quality data are being obtained on selected plots as well.

Our research is demonstrating that mixture responses can vary considerably from farm to farm, so the best test of mixture potential is to experiment with grass species and varieties on a small scale on your own farm.